CO2-focused breeding can arm crops for food fight

Growth of modern farmed rice varieties rise proportionally less when CO2 levels go up than wild types. Lewis Ziska and his colleagues said that more effort needs to be made in plant breeding to make sure crops benefit from higher CO2 levels. Credit: Héctor de Pereda/Flickr

While CO2 emissions from humans burning fossil fuels are wrapping the world in a worryingly warming blanket, they could also help make our crops grow faster. But more direct effort is needed to make the most of this chance, say Lewis Ziska from the US Department of Agriculture and an international team of scientists. “Plant breeders often assume that on-going breeding efforts, for example for pest or disease resistance, would by themselves lead to adaptation to any rise in background CO2 levels,” Lewis told Simple Climate. “We’ve shown that this is not the case.”

Throughout the 20^th century crop breeding has been one part of a green revolution that has made farmers today able to produce much more food from their fields. But Ziska notes that these improvements in crop yields are slowing. Though climate change and the droughts it brings makes this problem even harder, the gas driving it could provide a way out.

“The gains of the green revolution with respect to population growth have ended,” Ziska said. “As agricultural scientists our goal is to ensure a safe and nutritious supply of food.  It is clear we will have to do so with fewer resources, specifically arable land, water and fertilizer. We have long recognized that CO2 is, by itself, a resource as it supplies plants with carbon, the basic building block for growth. Hence we are urging a systematic active effort in selecting cereal lines that could respond to rising CO2 levels by increasing their yields.”

This view springs from a wide range of evidence Ziska and his colleagues brought together in a paper published in the research journal Proceedings of the Royal Society B this week. This included Ziska’s own research showing how CO2 concentrations affected wheat bred during the 20^th century, when CO2 rose from around 290 parts per million (ppm) to 380 ppm. That study showed that higher CO2 concentrations increased the amount of wheat produced by forms developed nearer to 1900 more than modern varieties.

Bred to ensure enough bread

Average change by decade in percent growth of the basic cereals barley, corn, millet, oat, rice, rye, sorghum, wheat as directly consumed by the human population,. not used for biofuels or animal feed and the average change by decade in percent population growth. Gains in cereal production over population represent the ‘green revolution’ of the 1960s. Around 2003, net percent gains in cereals and those in population were roughly equivalent, and the green revolution ended, Ziska’s team writes. Data are from FAO statistics. Credit: USDA

“We also observed another interesting trend when we compared cultivated rice with wild or weedy rice over a similar range of CO2 concentrations, from 300 to 400 ppm,” Ziska said. “There was little difference in their growth at 300 ppm CO2, but at today’s 400 ppm, the weedy rice significantly outperformed the domesticated, cultivated, rice lines.” This hints at the kind of natural selection that drives evolution preferring the wild varieties, Ziska said, which may be because they have a more varied genetic make-up.

Overall their findings suggest that breeding cereals crops better suited to the modern environment could reduce pressure on food supply in the near future. “Ongoing selection for greater conversion of carbon into seed yield may be a quick means to begin to increase cereal seed yields globally, within 5-10 years,” he said. “This comes at a time when the food needs of the 7 billion individuals on the planet in 2010 extra 2 billion expected by 2040 are critical.The globe experienced a food crisis in 2007-2008 and in 2010-2011.  The current, extensive drought in the US, which is the world’s largest food exporter, suggests that food will again be an issue in 2012-2013. “

But taking this chance needs those who pay for and otherwise back research to notice it, and fully understand the problem it solves. “Scientists from around the globe recognize the need for greater resources, human, natural and monetary, directed to agricultural research,” Ziska said. “We need this direction if we are to begin to implement not only the suggestions in this paper, but the numerous technological and scientific innovations that are necessary to address the issue of food security and sustainability. These resources can, and should be, part of an integrated effort among governments, non-governmental organisations, academic and private interests. Unfortunately, at the moment my own sense is that we seem to be in stasis, with little recognition of the scope of the problem, and little willingness to address it beyond the rhetoric.”